1. Field of the Invention
This invention relates to apparatus for the selective plating of repetitive surface portion(s), i.e., spots or stripes on continuous strip. The strip is advanceable continuously at a high velocity through a cell passing an anode and manifold in which a flowing electrolyte provides the metallic ions for plating. The apparatus is used to mask and plate conductive pads or the like on a workpiece strip.
2. Description of the Prior Art
So called "stripe plating" has been employed on metal or plastic strips, bonded connector pins and sockets and lead frames, individual increments of which are usable in making electrical or electronic parts or components. Plating cells which plate metal on strips and which are indexed or continuously moved as they unroll from a reel have been developed and sold. Typical of these are those cells seen in U.S. Pat. Nos. 4,029,555; 4,220,506; 4,378,283 (Seyffert and Laverty); 4,409,924 (Laverty et al.) and 3,746,630. U.S. Pat. Nos. 3,819,502; 3,855,108; 3,962,063; 3,986,945; and 4,036,725 utilize an insulatively-faced wheel over which a strip passes for plating. In indexing, i.e., step and repeat systems, it has been estimated that 30% of the time is taken in performing the indexing so that only 70% of the time is available for production. Thus continuous systems are advantageous.
The Robbins and Craig Company has developed a reel-to-reel automatic masking and plating cell system called Syncro-Plat III for plating one or more stripes of precious metal on one or both sides of a metal strip. This device operates at up to 30 feet per minute utilizing at least two moving belts each belt having belt segments spaced from each other to form a slot so that electrolyte can pass through the slot as the strip is being conveyed through the cell by the driving action of the belts in contact with the strip to be stripe plated. The belts have a metal back-up layer which is apertured, so that electrolyte from a fixed manifold passes through a series of holes in the manifold through the back-up layer apertures and belt slot(s) to the workpiece strip held between the belts. One or more manifolds fixed during operation are provided within the circumference of the driven belts which convey electrolyte to the strip surfaces to be plated. Spent electrolyte drains out the ends of the belt apparatus adjacent the strip entrance and exits between the pair of facing belts. Such belt system has been found advantageous over the wheel systems previously employed, in that the workpiece strip is "clamped" by and between facing moving belts so that the strip is not stretched or bent. This is particularly evident when plating thin metal foils or lace-like stamped or formed strips.
Various of the prior art devices cause slippage of the strip or unwanted drag or scraping of the strip as it passes through the plating station. These devices also generally suffer from electrolyte leakage, particularly the Syncro-Plat III device where electrolyte, either by design or seal failure, sprays out and causes a degree of undesirable plating or "discolor" on portions of the strip where no plating or contamination is desired. Likewise indexed devices oft times cause double plating thicknesses at certain portions of the strip. Some prior art cells are not operable with spliced strips.